1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly to a semiconductor device having a constitution which is capable of corresponding to further increases in the number of external terminals and a manufacturing method thereof.
2. Description of Related Art
A package of an equal size to a semiconductor chip cut from a semiconductor wafer is generally known as a CSP (Chip Size Package). Further, a CSP obtained when a semiconductor chip formed on a semiconductor wafer is packaged in the form of the original semiconductor wafer is known as a WCSP.
In Japanese Unexamined Patent Application Publication 2000-299406, a semiconductor device which is formed as a CSP and constituted to prevent warping generated from a wiring layer and metal posts formed on an IC circuit and changes in the characteristic of the IC circuit generated by heat and stress received from the soldering is disclosed.
This semiconductor device comprises a wiring layer having Cu as its main material which is connected to pads made of a metallic material and extends over the chip surface. Metal posts are formed in one region of the wiring layer. An insulating resin layer which covers the chip surface, including the wiring layer, is provided such that the surface of the metal posts protrudes therefrom.
The metal posts are positioned outside of an electrode pad group and the region surrounded by the electrode pad group. Solder bumps or solder balls are fixed onto the metal posts. The solder bumps or solder balls are formed on the periphery of the chip.
The number of external terminals provided on the mounting face of the semiconductor device, or in other words the pin count, is determined according to the size of the mounting face and the pitch of the external terminals (the distance between two adjacent terminals) The number of pins on the mounting face increases as the size of the mounting face increases or as the pitch of the external terminals decreases. Increasing the number of pins on the mounting face in this manner is known as increasing the pin count.
In general, the pitch of the external terminals is specified on the side of the user who is to use the semiconductor device. Hence even if the external terminal pitch of the semiconductor device is reduced with the size of the mounting face remaining at a fixed size such that the pin count is increased, and the semiconductor device is provided to a user with the pin count thus increased, circumstances may arise in which the provided semiconductor device cannot be used on the user side. Moreover, when the external terminal pitch is reduced with the size of the mounting face remaining at a fixed size, the pin count that can be realized when the pin count is increased is limited.
Alternatively, increasing the size of the mounting face while keeping the external terminal pitch at a fixed value has been considered as a method of realizing a high pin count. In the case of a semiconductor device having a WCSP constitution, the size of the semiconductor chip surface and the size of the mounting face are equal. Hence if the size of the mounting face is increased in a semiconductor device having a WCSP constitution, the size of the semiconductor chip surface is also increased.
The semiconductor chip comprises a circuit element. As is well-known, this circuit element is provided to perform a desired electrical operation in accordance with the design, for example to serve as an integrated circuit. Modifying the design of the circuit element formed on the semiconductor chip has been considered in order to increase the size of the semiconductor chip surface. However, if the design of the circuit element is modified, the manufacturing cost of the semiconductor chip rises.
If the size of the semiconductor chip surface is increased without modifying the design of the circuit element, the semiconductor chip can only be used in the packaging of a WCSP constitution having the target mounting face size, and packaging constitutions other than this WCSP constitution cannot be applied to the semiconductor chip. In this case also, rises in the manufacturing cost of the semiconductor chip are inevitable.
Hence, to realize a high pin count by increasing the size of the mounting face with the external terminal pitch remaining at a fixed value, a packaging constitution other than a WCSP must be applied to the semiconductor chip in other words, according to a conventional semiconductor device having a WCSP constitution, the problems described above make the realization of a high pin count difficult.
An object of this invention is to provide a semiconductor device having a WCSP constitution in which a high pin count can be realized easily by increasing the size of the mounting face, and a manufacturing method therefor.
A further object of this invention is to increase the operational stability of a semiconductor device having such a constitution by providing a semiconductor device having one or both of a constitution which is capable of reducing power source inductance caused by power bounce and a constitution which is suitable for high speed signal transmission, and a manufacturing method therefor.